Friday, 11 May 2012

It's Raining Gardens.

I have been thinking about our soggy drought.  Obviously our weather patterns are changing and seem to be becoming more extreme.  It is a sad fact of life and our gardens and gardening habits need to adapt to get the best out of what is happening.  It now seems 'normal' to have very dry periods broken by extremely wet intervals.

All the recent press about Drought Gardening is well and good, but I don't think it quite covers what is happening here and now, in Devon.  We can certainly plant drought tolerant species but we need to ensure that they either have very free draining soil for when the deluges arrive (assuming they are desert adapted), or that they are able to cope with extreme wet, such as we have had in the past few days.

Given our recent weather it is quite likely to be raining as you read this.  If it is, look outside at your terrace or a paved area.  For every 1 millimetre of rain that falls on a square metre of paving 1 litre of water will be collected.  So in a ‘standard storm’ (or frog-strangling downpour) 30 litres of water will fall on every square metre of garden - paved or otherwise.  That's a lot of water.

All this has to go somewhere.  It can either go straight into the drains, which can easily become overwhelmed and cause flooding, or we can use it to create a beautiful type of garden called a Rain Garden.
The idea of designing a garden, specifically as a Rain Garden is relatively new and has been developing only over the past 20 years.  A Rain Garden tries to keep as much rain water as possible out of the sewage and mains drainage systems allowing it to drain away naturally and slowly. 

Rain Gardens have a lot of points in their favour:

·         They look beautiful.
·         They are good for wildlife.
·         They help prevent floods.
·         They help top up the aquifers.

Rain Gardens can be designed in either a formal or informal style which must look attractive in both wet and dry weather.

The basic principal is to keep as much rainwater as possible on the property and to keep it visible. 

The starting point is rain coming off a roof or terrace.  This can go down the usual guttering or rain chains and can then be gathered into storm water planters.  These can be in any style at all, as long as they have an overflow mechanism for when there is too much water for them to absorb.  When this happens the next stage of water management starts.  This can be in the form of rills or streams which will direct the water from the planters into the Rain Garden itself.  This is basically an absorbent planted depression or hollow which acts as a big sponge.  It needs to have very well drained soil and plants that can cope with being soaked for periods.  If there is so much rain that this area overflows the water can then be directed to a pond which can hold the rainwater until it can gently drain away naturally over a period of days.  Alternatively the pond can be lined and used as a semi permanent feature in the garden. 

This style of garden is flexible enough to cope with periods of drought but will really come into its own when the heavens open and it becomes a watery haven.  You could even look at it as getting two gardens for the price of one, which surely has to be a good thing.